springmvc之@ModelAttribute的用法

àì夳堔傛蜴生んèń 2022-12-04 09:19 183阅读 0赞

## 1：用在controller中的非handler方法上 ##

如果将注解`@ModelAttribute`定义在controller中的非handler方法上，则在调用controller中的handler之前会先执行该方法，可以针对handler做一些拦截工作，如初始化，验证等。

### 1.1：定义类 ###

@Controller
    @RequestMapping("/myModelAttribute")
    public class MyModelAttributeController {
    
    	@ModelAttribute
    	public void runBecauseModelAttribute() {
    		System.out.println("****runBecauseModelAttribute****");
    	}
    
    	@RequestMapping("/test1")
    	@ResponseBody
    	public String test1() {
    		return "test modelattribue on method";
    	}
    }

### 1.2：访问`/test1`测试 ###

![浏览器访问test1接口][test1]  
控制台打印：

![在这里插入图片描述][20200907182954786.jpg_pic_center]

## 2：为view准备统一的数据 ##

通过在方法上加注解并指定value的方式，来为view设置可展示的数据。

### 2.1：controller代码 ###

package dongshi.controller.modelattribute;
    
    import java.util.ArrayList;
    import java.util.List;
    import org.springframework.scheduling.support.SimpleTriggerContext;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.ModelAttribute;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    @Controller
    @RequestMapping("/myModelAttribute")
    public class MyModelAttributeController {
    	private static List<String> myList = new ArrayList<String>();
    	{
    		myList.add("111");
    		myList.add("222");
    		myList.add("333");
    	}
    	
    	@ModelAttribute("accounts")
    	public List<String> returnMyList() {
    		System.out.println(myList);
    		return myList;
    	}
    
    	@RequestMapping("/test2")
    	public String test2() {
    		return "modelattribute/myList.jsp";
    	}
    }

### 2.2：jsp代码 ###

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
    <html>
    <head>
        <title>validate user</title>
    </head>
    <body>
    ${accounts}
    </body>
    </html>

### 2.3：测试 ###

![在这里插入图片描述][20200907194021721.jpg_pic_center]

## 3：使用对象接收页面数据 ##

### 3.1：定义表单 ###

<%--
      Created by IntelliJ IDEA.
      User: cj
      Date: 2020/9/7
      Time: 19:44
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
    <form action="${pageContext.request.contextPath}/myModelAttribute/test4" method="post" enctype="multipart/form-data">
        <input type="text" name="name" placeholder="人名"><br><br>
        <input type="text" name="age" placeholder="人年龄"><br><br>
        <input type="submit" value="提交"/>
    </form>
    
    </body>
    </html>

### 3.2：定义接口 ###

package dongshi.controller.modelattribute;
    
    import java.util.ArrayList;
    import java.util.List;
    import org.springframework.scheduling.support.SimpleTriggerContext;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.ModelAttribute;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    @Controller
    @RequestMapping("/myModelAttribute")
    public class MyModelAttributeController {
    	@RequestMapping("/test3")
    	public String test3() {
    		return "modelattribute/myPeopleInfo.jsp";
    	}
    	
    	@RequestMapping("/test4")
    	@ResponseBody
    	public String test4(@ModelAttribute PeopleInfo peopleInfo) {
    		System.out.println(peopleInfo);
    		return peopleInfo.toString();
    	}
    }

### 3.3：访问测试 ###

*  访问页面  
    ![在这里插入图片描述][20200907195041435.jpg_pic_center]
 *  录入信息  
    ![在这里插入图片描述][20200907195112602.jpg_pic_center]
 *  提交  
    ![在这里插入图片描述][20200907195138180.jpg_pic_center]

## 最后：都让开，我要喝瑞幸 ##

![在这里插入图片描述][20200828090303329.png_pic_center]

[test1]: /images/20221123/3531d97559d141fe8d6c28c3213002da.png
[20200907182954786.jpg_pic_center]: /images/20221123/815a54d35a484613827043df534d5e83.png
[20200907194021721.jpg_pic_center]: /images/20221123/d5a7bf29a9234c83abd0670e9bb880c4.png
[20200907195041435.jpg_pic_center]: /images/20221123/5c807d3ead26439c95ef20cc5bde58e7.png
[20200907195112602.jpg_pic_center]: /images/20221123/28af2c752b2c4097a959980dd322613d.png
[20200907195138180.jpg_pic_center]: /images/20221123/e95860f0e2bf4c538da55c6ac2a3c198.png
[20200828090303329.png_pic_center]: /images/20221123/fe46ff743e9f48b89c6a75b477527ec1.png